(19)
(11)EP 3 242 338 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.04.2020 Bulletin 2020/18

(21)Application number: 14909327.0

(22)Date of filing:  29.12.2014
(51)International Patent Classification (IPC): 
H01L 35/34(2006.01)
C01B 19/00(2006.01)
H01L 35/16(2006.01)
(86)International application number:
PCT/CN2014/095376
(87)International publication number:
WO 2016/106514 (07.07.2016 Gazette  2016/27)

(54)

THERMOELECTRIC MATERIAL, AND PREPARATION METHOD THEREFOR AND APPLICATION THEREOF

THERMOELEKTRISCHES MATERIAL SOWIE HERSTELLUNGSVERFAHREN DAFÜR UND ANWENDUNG DAVON

MATÉRIAU THERMOÉLECTRIQUE, PROCÉDÉ DE PRÉPARATION DE CELUI-CI ET APPLICATION DE CELUI-CI


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(43)Date of publication of application:
08.11.2017 Bulletin 2017/45

(73)Proprietor: Fujian Institute Of Research On The Structure Of Matter, Chinese Academy Of Sciences
Fuzhou, Fujian 350002 (CN)

(72)Inventors:
  • WU, Liming
    Fuzhou Fujian 350002 (CN)
  • LIN, Hua
    Fuzhou Fujian 350002 (CN)
  • CHEN, Ling
    Fuzhou Fujian 350002 (CN)

(74)Representative: Ter Meer Steinmeister & Partner 
Patentanwälte mbB Nymphenburger Straße 4
80335 München
80335 München (DE)


(56)References cited: : 
CA-A1- 2 307 239
CN-A- 102 403 445
CN-A- 1 546 369
CN-A- 103 050 618
  
  • LI JING ET AL: "CsAg5Te3: a new metal-rich telluride with a unique tunnel structure", JOURNAL OF ALLOYS AND COMPOUNDS, vol. 218, no. 1, 15 February 1995 (1995-02-15), pages 1-4, XP029116353, ISSN: 0925-8388, DOI: 10.1016/0925-8388(94)01359-4
  • JING, LI ET AL.: 'CsAg5Te3: a new metal-rich telluride with a unique tunnel structure' JOURNAL OF ALLOYS AND COMPOUNDS vol. 218, no. 1, 15 February 1995, pages 1 - 4, XP029116353
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

Technical Field



[0001] The present application relates to a method for preparing a CsAg5Te3 crystal material, a method for preparing a densified bulk thermoelectric material comprising the CsAg5Te3 crystal material and the use of the material in a thermoelectric converter.

Technical Background



[0002] Under solid-state condition, thermoelectric materials can realize a direct interconversion of thermal and electrical energy by motion of internal carriers (electrons or holes) and is a green and environmental protective energy conversion material.

[0003] The work efficiency of thermoelectric devices is mainly determined by the performance of thermoelectric materials. The dimensionless figure-of-merit ZT is an important index to characterize the conversion efficiency of thermoelectric materials. The formula for calculating the dimensionless figure-of-merit is



[0004] Where, S is the Seebeck coefficient; and σ is the electric conductivity; and T is the absolute temperature; and κ is the total thermal conductivity. S2σ is also known as power factor (abbreviated as PF), used for characterization of electrical properties of thermoelectric materials; and the total thermal conductivity κ is comprised of two parts: lattice thermal conductivity (abbreviated as κlat) and electron thermal conductivity (abbreviated as κele).

[0005] In 1995, Li et al. reported a crystal material CsAg5Te3 (J. Solid State Chem.1995, 218:1-4). In this paper, the synthesis of pure phase CsAg5Te3 adopts two-step method. Firstly, the binary phase Cs2Te is synthesized, and then the target product is obtained by reacting with Ag. The total reaction process is taken 10 days.

Summary of the Invention



[0006] According to an aspect of the present application, a thermoelectric material with a dimensionless figure-of-merit ZT(700K) of 1.6 is provided. The thermoelectric material contains CsAg5Te3 crystal material. The CsAg5Te3 crystal material is at least one selected from the CsAg5Te3 crystal material prepared by any method provided in the present application, or the CsAg5Te3 crystal material prepared by other methods. Preferably, the thermoelectric material is composed of the CsAg5Te3 crystal material. The framework structure of CsAg5Te3 crystal material is formed by Ag and Te. It has three-dimensional channel structure and Cs is located in three-dimensional channel.

[0007] According to another aspect of the present application, a method for preparing CsAg5Te3 crystal material is provided. Using the method, CsAg5Te3 crystal material product with high purity is one-step synthesized, and synthesis time is greatly shortened.

[0008] The method for preparing CsAg5Te3 crystal material comprises that CsAg5Te3 crystal material is obtained by placing a raw material containing cesium element, silver element and tellurium element under a vacuum condition and using high temperature solid phase method.

[0009] Preferably, the mole ratio of cesium element, silver element and tellurium element in the raw material is
Cs : Ag : Te = 1 : 4.9∼5.1 : 2.9∼3.1.

[0010] More preferably, the mole ratio of cesium element, silver element and tellurium element in the raw material is
Cs : Ag : Te = 1 : 5 : 3.

[0011] Preferably, in the raw material, the silver element is from silver elementary substance; and the cesium element is from cesium elementary substance; and the tellurium element is from tellurium elementary substance. More preferably, in the raw material, silver elementary substance is located between cesium elementary substance and tellurium elementary substance.

[0012] Preferably, the condition of high temperature solid phase method is that the raw material is kept in a temperature range from 750°C to 950°C for no more than 48 hours. Preferably, the condition of high temperature solid phase method is that the raw material is kept in a temperature range from 800°C to 900°C for no more than 24 hours.

[0013] As a preferred embodiment, the method for preparing CsAg5Te3 crystal material includes at least steps as follows:
  1. a) placing cesium elementary substance, silver elementary substance and tellurium elementary substance in sequence in a vessel;
  2. b) after vacuumizing and sealing, keeping the vessel in a temperature range from 750°C to 950°C for no more than 48 hours to obtain the CsAg5Te3 crystal material.


[0014] Preferably, in step a), the cesium elementary substance does not contact with the tellurium elementary substance.

[0015] According to another aspect of the present application, a method for preparing a densified bulk thermoelectric material is provided, wherein the densified bulk thermoelectric material is obtained by hot-pressing sintering of the CsAg5Te3 crystal material obtained using any of the above-mentioned method; which is that the CsAg5Te3 crystal material is kept in a temperature range from 400°C to 500°C and in a pressure range from 60 MPa to 110 MPa for not less than 30 min to the obtain densified bulk thermoelectric material.

[0016] Preferably, the time of hot-pressing sintering is in a time range from 30min to 90min.

[0017] According to another aspect of the present application, a thermoelectric material is provided. At 700K, the thermal conductivity of the thermoelectric material can reach 0.19 W/m·K, and the electric conductivity can reach 53 S/cm, and the Seebeck coefficient can reach 295 µV/K, and the optimum dimensionless figure-of-merit ZT can reach 1.6. Meanwhile, the thermoelectric material has a high stability and can be recycled for many times.

[0018] The thermoelectric material contains CsAg5Te3 crystal material; and the weight percentage content of the CsAg5Te3 crystal material prepared by any of the above-mentioned method in total CsAg5Te3 crystal material contained in thermoelectric material ranges from 0wt% to 100wt%. Preferably, the weight percentage content of the CsAg5Te3 crystal material prepared by any of the above-mentioned method in total CsAg5Te3 crystal material contained in thermoelectric material is greater than 0wt%. More Preferably, the weight percentage content of the CsAg5Te3 crystal material prepared by any of the above-mentioned method in total CsAg5Te3 crystal material contained in thermoelectric material is 100wt%.

[0019] The thermoelectric material contains CsAg5Te3 crystal material prepared by any of the above-mentioned method and/or the densified bulk thermoelectric material prepared by any of the above-mentioned method.

[0020] Preferably, the thermoelectric material is composed of CsAg5Te3 crystal material prepared by any of the above-mentioned method and/or the densified bulk thermoelectric material prepared by any of the above-mentioned method.

[0021] According to another aspect of the present application, a thermoelectric converter is provided. The thermoelectric converter contains CsAg5Te3 crystal material. Preferably, the weight percentage content of the CsAg5Te3 crystal material prepared by any of the above-mentioned method in total CsAg5Te3 crystal material contained in thermoelectric converter ranges from 0wt% to 100wt%. Preferably, the weight percentage content of the CsAg5Te3 crystal material prepared by any of the above-mentioned method in total CsAg5Te3 crystal material contained in thermoelectric converter is greater than 0wt%. More Preferably, the weight percentage content of the CsAg5Te3 crystal material prepared by any of the above-mentioned method in total CsAg5Te3 crystal material contained in thermoelectric converter is 100wt%.

[0022] According to another aspect of the present application, a thermoelectric converter is provided. The thermoelectric converter contains CsAg5Te3 crystal material prepared by any of the above-mentioned method and/or the densified bulk thermoelectric material prepared by any of the above-mentioned method.

[0023] The advantages of the present application include at least:
  1. (1) At 700K, the thermal conductivity of the thermoelectric material provided in the present application can reach 0.19 W/m·K, and the electric conductivity can reach 53 S/cm, and the Seebeck coefficient can reach 295 µV/K, and the optimum dimensionless figure-of-merit ZT can reach 1.6.
  2. (2) The thermoelectric material provided in the present application has high stability and can be recycled for many times.
  3. (3) The method for preparing CsAg5Te3 crystal material provided in the present application is a one-step synthesis method, which can greatly reduce the synthesis time and obtain the product with high purity at the same time.

Brief Description of the Drawings



[0024] 

Figure 1 is XRD powder diffraction spectrum of Sample 1 powder: (a) is the theoretical powder X-ray diffraction spectrum of CsAg5Te3; (b) is the powder X-ray diffraction spectrum of the Sample 1 powder obtained by experimental measure.

Figure 2 is a graph showing the relationship of electrothermal transport properties to temperature of Samples 1 to 4: (a) shows the relationship of electric conductivity to temperature; (b) shows the relationship of Seebeck coefficient to temperature; (c) shows the relationship of power factor to temperature; (d) shows relationship of thermal conductivity to temperature.

Figure 3 is a graph showing the relationship of Dimensionless figure-of-merit to temperature of Samples 1 to 4.

Figure 4 is a graph showing the relationship of the electrical transport property to temperature of Sample 1 recycled for once, twice and three times: (a) shows the relationship of electric conductivity to temperature; (b) shows the relationship of Seebeck coefficient to temperature.


Detailed Description of the Embodiment



[0025] The present application will be further described by combining with Examples. It should be understand that these Examples are only used to illustrate the present application and not to limit the scope of the present application.

[0026] In the Examples, the X ray powder diffraction analysis of the samples were determined using a D/MAX2500 X-ray Diffractometer of Rigaku Corporation, with Cu target, Kα radiation source (λ=0.154184 nm).

[0027] The thermal conductivities were measured on a LFA427 thermal conductivity meter of German Netzsch.

[0028] The electric conductivities and Sebecke coefficients were measured using a ZEM-3 thermoelectric evaluation system of the Japanese ULAC-RIKO, Inc.

[0029] The hot pressing sintering was carried out in ZTY-15-20 hot pressing sintering furnace of Shanghai Chenxin Electric Furnace Co., LTD.

[0030] In the Examples, cesium elementary substance was a liquid cesium with purity of 99.98% purchased from Alfa Aesar (China) Chemical Co. LTD.; and silver elementary substance was a silver powder with purity of 99.999% purchased from Sinopharm Chemical Reagent Co., LTD.; and tellurium elementary substance was a tellurium block with purity of 99.999% purchased from Sinopharm Chemical Reagent Co., LTD.

Example 1 Preparation of Samples 1 Powder to 4 Powder



[0031] The liquid cesium, silver powder and tellurium block were placed in a quartz reaction tube in sequence. After being vacuumized to 10-2Pa, the quartz reaction tube was sealed with oxyhydrogen flame and then placed in a high temperature furnace. And then it spent 10 hours for increasing the temperature of the high temperature furnace from room temperature to the solid melting temperature. After keeping the temperature at the solid melting temperature for a solid melting time, the temperature was naturally cooled to room temperature, grinding to obtain the CsAg5Te3 crystal material powder samples. The relationship of number of Samples with molar ratios in the raw material, solid melting temperatures and solid melting times were shown in Table 1.
Table 1
SamplesMolar Ratio in the raw materialSolid Melting Temperature (°C)solid melting time (h)
1 Powder Cs : Ag : Te 850 20
= 1 : 5 : 3
2 Powder Cs : Ag : Te 950 12
= 1 : 4.9 : 2.9
3 Powder Cs : Ag : Te 900 24
= 1 : 5.05 : 3.05
4 Powder Cs : Ag : Te 750 48
= 1 : 5.1 : 3.1

Example 2 Structural Characterization of the Samples 1 Powder to 4 Powder



[0032] The X-ray powder diffraction analysis (XRD) of Samples 1 Powder to 4 Powder were determined. The results indicated that Samples 1 Powder to 4 Powder prepared in Example 1 all were CsAg5Te3 crystal samples with high purity. The typical XRD spectrum was the XRD spectrum of Sample 1 Powder, which was shown in Figure 1. In Figure 1, (a) is the theoretical powder X-ray diffraction spectrum of CsAg5Te3 and (b) is the powder X-ray diffraction spectrum of the Sample 1 powder obtained by experimental measure. It showed that the experimental spectrum was high consistent with the theoretical spectrum simulated from single crystal data, indicating that the sample prepared was with a very high purity. XRD spectra of Sample 2 Powder, Sample 3 Powder and Sample 4 Powder were similar to Figure 1, which showed that each corresponding peak had the same peak position and the ±5% difference of peak intensity.

Example 3 Preparation of densified bulk Samples 1 to 4



[0033] The Samples 1 Powder to 4 Powder were put into a hot pressing sintering furnace respectively, to obtain the densified bulk samples, and the densified bulk samples were respectively recorded as Sample 1 to Sample 4. The relationship of number of Samples with the conditions of hot pressing sintering were shown in Table 2
Table 2
SamplesPressure (MPa)Temperature (°C)Time (min)
1 110 400 30
2 100 430 40
3 80 460 60
4 60 500 90

Example 4 Measurement of Thermoelectric Properties of Samples 1 to 4



[0034] The thermoelectric properties of Samples 1 to 4 obtained in Example 3 were measured us a thermoelectric evaluation system. The detailed process was as follows: cutting the densified bulk Samples 1 to 4 by hot pressing sintering into a disk with 10 mm diameter and 2 mm thickness, respectively, to be used in the measurement of thermal conductivity; and cutting the densified bulk Samples 1 to 4 into a cuboid of 2mm×3mm×10mm, respectively, to be used in the measurement of Seebeck coefficient. The relationship of electrothermal transport properties to temperature of Samples 1 to 4 was shown in Figure 2. And Figure 2 (a) had shown the relationship of electric conductivity to temperature; and Figure 2 (b) had shown the relationship of Seebeck coefficient to temperature; and Figure 2 (c) had shown the relationship of power factor to temperature; and Figure 2 (d) had shown relationship of thermal conductivity to temperature. It indicated that Samples 1 to 4 all have moderate electric conductivity and high Seebeck coefficient and the lowest thermal conductivity comparing with the similar thermoelectric materials which currently exist.

[0035] The graph showing the relationship of Dimensionless figure-of-merit to temperature of Samples from 1 to 4 had been shown in Figure 3. It indicated that at 700K, the optimum dimensionless figure-of-merit ZT could reach 1.6, which is the highest vale among polycrystal thermoelectric materials without doping modification which currently exist. The ZT of the thermoelectric material provided in the present application is expected to be improved through further optimization.

Example 5 Measurement Thermoelectric Properties of the recycled Sample 1



[0036] The thermoelectric properties of the recycled Sample 1 were measured. The detailed process was as follows: cutting the densified bulk Sample 1 into a cuboid of 2mm×3mm×10mm; and then placing the cuboid in the ZEM-3 thermoelectric evaluation system to in-situ measure for 3 times .

[0037] The relationship of the electrical transport property to temperature of Sample 1 had been shown in Figure 4. And (a) had shown the relationship of electric conductivity to temperature; and (b) had shown the relationship of Seebeck coefficient to temperature. It indicated that the sample has high stability and recyclability.

[0038] It will be understood that the foregoing Examples are only some examples of the present application, rather than limit the present application in any form. Although the optimized examples of the present application are illustrated as above, they are not intended to limit the present application. In view of the instant disclosure, modifications or changes may be made by those skilled in the art and those modifications or changes are equivalent embodiments of the present application, falling into the scope of the appended claims.


Claims

1. A method for preparing CsAg5Te3 crystal material, the CsAg5Te3 crystal material being obtained by placing a raw material containing cesium element, silver element and tellurium element under a vacuum condition and using high temperature solid phase method, characterized in that
in the raw material, the silver element is from silver elementary substance; and the cesium element is from cesium elementary substance; and the tellurium element is from tellurium elementary substance,
in the raw material, the silver elementary substance is located between the cesium elementary substance and the tellurium elementary substance, and
the condition of the high temperature solid phase method is that the raw material is kept in a temperature range from 750°C to 950°C for no more than 48 hours.
 
2. A method for preparing CsAg5Te3 crystal material according to claim 1, wherein the mole ratio of cesium element, silver element and tellurium element in the raw material is
Cs : Ag : Te = 1 : 4.9∼5.1 : 2.9∼3.1.
 
3. A method for preparing CsAg5Te3 crystal material according to claim 1, wherein the mole ratio of cesium element, silver element and tellurium element in the raw material is
Cs : Ag : Te = 1 : 5 : 3.
 
4. A method for preparing a densified bulk thermoelectric material, wherein the densified bulk thermoelectric material is obtained by hot-pressing sintering of the CsAg5Te3 crystal material obtained using the method according to claim 1; which is that the CsAg5Te3 crystal material is kept in a temperature range from 400°C to 500°C and in a pressure range from 60 MPa to 110 MPa for not less than 30 min to the obtain densified bulk thermoelectric material.
 
5. Use of the CsAg5Te3 crystal material prepared by any method according to claims from 1 to 3 and/or the densified bulk thermoelectric material prepared by any method according to claim 4 for a thermoelectric material.
 
6. Use of the CsAg5Te3 crystal material prepared by any method according to claims from 1 to 3 and/or the densified bulk thermoelectric material prepared by any method according to claim 4 for a thermoelectric converter.
 


Ansprüche

1. Verfahren zur Herstellung von CsAg5Te3-Kristallmaterial, wobei das CsAg5Te3-Kristallmaterial erhalten wird, indem ein Rohmaterial, das elementares Cäsium, elementares Silber und elementares Tellur enthält, unter Vakuumbedingungen und unter Verwendung einer Hochtemperatur-Festphasenmethode eingesetzt wird,
dadurch gekennzeichnet, dass
im Rohmaterial das elementare Silber aus elementarer Silbersubstanz; und das elementare Cäsium aus elementarer Cäsiumsubstanz; und das elementare Tellur aus elementarer Tellursubstanz ist,
sich im Rohmaterial die elementare Silbersubstanz zwischen der elementaren Cäsiumsubstanz und der elementaren Tellursubstanz befindet, und
die Bedingung der Hochtemperatur-Festphasenmethode ist, dass das Rohmaterial nicht länger als 48 Stunden in einem Temperaturbereich von 750°C bis 950°C gehalten wird.
 
2. Verfahren zur Herstellung von CsAg5Te3-Kristallmaterial nach Anspruch 1, wobei das Molverhältnis von elementarem Cäsium, elementarem Silber und elementarem Tellur im Rohmaterial
Cs : Ag : Te = 1 : 4,9∼5,1 : 2,9∼3,1
beträgt.
 
3. Verfahren zur Herstellung von CsAg5Te3-Kristallmaterial nach Anspruch 1, wobei das Molverhältnis von elementarem Cäsium, elementarem Silber und elementarem Tellur im Rohmaterial
Cs : Ag : Te = 1 : 5 : 3.
beträgt.
 
4. Verfahren zur Herstellung eines verdichteten thermoelektrischen Massenmaterials, wobei das verdichtete thermoelektrische Massenmaterial durch Heißpresssintem des CsAg5Te3-Kristallmaterials erhalten wird, das unter Verwendung des Verfahrens nach Anspruch 1 erhalten wird; das heißt, dass das CsAg5Te3-Kristallmaterial in einem Temperaturbereich von 400°C bis 500°C und bei einem Druckbereich von 60 MPa bis 110 MPa für nicht weniger als 30 min gehalten wird, um das verdichtete thermoelektrische Massenmaterial zu erhalten.
 
5. Verwendung des CsAg5Te3-Kristallmaterials, hergestellt durch ein Verfahren nach den Ansprüchen 1 bis 3, und/oder des verdichteten thermoelektrischen Massenmaterials, hergestellt durch ein Verfahren nach Anspruch 4, für ein thermoelektrisches Material.
 
6. Verwendung des CsAg5Te3-Kristallmaterials, hergestellt durch ein Verfahren nach den Ansprüchen 1 bis 3, und/oder des verdichteten thermoelektrischen Massenmaterials hergestellt durch ein Verfahren nach Anspruch 4, für einen thermoelektrischen Konverter.
 


Revendications

1. Procédé de préparation d'un matériau cristallin CsAg5Te3, le matériau cristallin CsAg5Te3 étant obtenu en plaçant une matière première contenant l'élément césium, l'élément argent et l'élément tellure dans une condition de vide et en utilisant une méthode en phase solide à haute température, caractérisé en ce que dans la matière première, l'élément argent est issu de substance élémentaire d'argent ; et l'élément césium est issu de substance élémentaire d'césium ; et l'élément tellure est issu de substance élémentaire de tellure,
dans la matière première, la substance élémentaire d'argent est située entre la substance élémentaire de césium et la substance élémentaire de tellure, et
la condition de la méthode en phase solide à haute température est que la matière première soit maintenue dans une plage de température de 750°C à 950°C pendant 48 heures au maximum.
 
2. Procédé de préparation d'un matériau cristallin CsAg5Te3 selon la revendication 1, le rapport molaire de l'élément césium, de l'élément argent et de l'élément tellure dans la matière première étant de
Cs : Ag : Te = 1 : 4,9∼5,1 : 2,9∼3,1.
 
3. Procédé de préparation d'un matériau cristallin CsAg5Te3 selon la revendication 1, le rapport molaire de l'élément césium, de l'élément argent et de l'élément tellure dans la matière première étant de
Cs : Ag : Te = 1 : 4,9∼5,1 : 2,9∼3,1 : Ag : Te = 1 : 5 : 3.
 
4. Procédé de préparation d'un matériau thermoélectrique massif densifié, dans lequel le matériau thermoélectrique massif densifié est obtenu par frittage sous pression à chaud du matériau cristallin de CsAg5Te3 obtenu en utilisant le procédé selon la revendication 1; c'est-à-dire que le matériau cristallin de CsAg5Te3 est maintenu dans une plage de température de 400°C à 500°C et dans une plage de pression de 60 MPa à 110 MPa pendant pas moins de 30 min pour obtenir le matériau thermoélectrique massif densifié.
 
5. Utilisation du matériau cristallin CsAg5Te3 préparé par le procédé selon l'une quelconque des revendications 1 à 3 et/ou du matériau thermoélectrique massif densifié préparé par le procédé selon la revendication 4 pour un matériau thermoélectrique.
 
6. Utilisation du matériau cristallin CsAg5Te3 préparé par le procédé selon l'une quelconque des revendications 1 à 3 et/ou du matériau thermoélectrique massif densifié préparé par le procédé selon la revendication 4 pour un convertisseur thermoélectrique.
 




Drawing

















Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Non-patent literature cited in the description